Previous studies from our laboratory suggested the possible importance of the Vitamin k-dependent procoagulant proteins in the thrombotic process that is involved in premature ischemic heart disease (IHD). This study proposes to examine whether an elevated plasma prothrombin level, associated with a variant prothrombin gene, is a risk factor for the development of premature IHD. The prothrombin gene mutation or variant is a G to A nucleotide transition at 20210 in the 3'untranslated(3'-UTR) region of the prothrombin gene, which is associated with a 25-30% increase in plasma prothrombin activity and with 3-fold increased risk of deep venous thrombosis. Other objectives of the proposal will be to prove whether this increase in prothrombin activity is associated with lipid metabolism or with an increase in any of the other three procoagulant Vitamin K-dependent proteins, in order to clarify the mechanism responsible for the elevated plasma prothrombin activity.